The present invention relates to a mobile terminal for a wireless telecommunication system, comprising a main body and a battery pack to be connected to the main body.
Mobile terminals for wireless telecommunication systems, such as portable telephones, laptops, notebooks, personal digital assistants and the like devices adapted for a wireless communication over an air interface as e.g. on the basis of the GSM and the UMTS system, usually comprise rechargeable battery packs for powering the mobile terminal. Such a battery pack is removably connected to a main body of the mobile terminal. The battery pack hereby comprises one or more rechargeable battery cells for powering the mobile terminal. In order to be able to stay synchronised to the respective telecommunication system as well as for internal and external control and other functions of the mobile terminal, a real time clock is provided in the main body. Hereby, when choosing and implementing a real time clock, contradictive requirements have to be met. On one hand, the real time clock should be highly accurate and as independent as possible from performance decreasing influences such as temperature drift, aging and the like, such that a correction and calibration of the real time clock means is not (permanently) necessary. This kind of highly accurate real time clock means, however, is usually a quite expensive device and has a quite high power consumption. On the other hand, a real time clock implemented in a mobile terminal should be as lightweight as possible and should not require large power for operation. This second kind of real time clocks, however, tend to be accurate enough.
In present mobile terminals for wireless telecommunication systems, real time clocks working on the basis of a 32 kHz crystal have proven to be a good tradeoff. These real time clocks are quite light and have a low power consumption, but still provide quite accurate time information. This is the reason why in many mobile terminals comprising a main body and a battery pack connected to the main body, the real time clock in the main body is working on the basis of a 32 kHz crystal or quartz device being not too expensive and consuming relatively little energy compared to highly accurate time base systems. Further, these real time clocks are quite small so that the space limitations of modern mobile terminals can be met. It has to be noted that in a real time clock, the frequency signal, as e.g. the 32 kHz frequency signal generated by a crystal or quartz device as frequency generating means is output as counts or clock cycles which are counted and then, by a corresponding processing means, processed into a real time information. In the main body of the mobile terminal, the processing means is e.g. a baseband chip receiving a frequency signal or frequency information on the basis of a frequency of 32 kHz (to be precise 32,768 kHz) from the quartz device. The baseband chip in the main body of the mobile terminal is e.g. adapted to control RF circuitry, display, audio circuitry, power management functionality and so on. The low frequency real time clock means operating on the basis of the 32 kHz frequency, however, is not sufficiently accurate for an exact synchronisation of the mobile terminal to the respective wireless telecommunication system, so that a highly accurate time base system, e.g. on the basis of a 65 MHz clock, is provided in the main body of the mobile terminal to enable an accurate synchronisation to the telecommunication system. However, this highly accurate time base is not operated constantly, but only during the mobile terminal is operating and communicating in the telecommunication system when the time frame timing of the system has to be accurately met. If the mobile terminal is not communicating in the wireless telecommunication system, the highly accurate time base goes to sleep and the low frequency real time clock is used for the operation of the mobile terminal.
Present mobile terminals further comprise a small back-up battery implemented in the main body for powering the low frequency real time clock during the battery pack is disconnected or has gone flat. The back-up battery powers the low frequency real time clock for a short period of time, e.g. several minutes, while the battery pack is disconnected and e.g. exchanged. In case that the battery pack is removed from the main body for a longer period of time, however, the real time information in the main body is lost since the back-up battery is not able to provide sufficient power for long time periods. For this reason, a further low frequency real time clock is provided in the battery pack of most present mobile terminals. The real time clock in the battery pack keeps operating while the battery pack is disconnected from the main body so that, when the battery pack is reconnected to the main body, the real time information from the battery pack is used to readjust the real time clock in the main body. The problem, however, is that no information is available about how accurate the real time clock in the battery pack is so that the processing means in the main body of the mobile terminal receiving real time clock information from a just connected battery pack cannot be sure if the received time information is reliable or not.
U.S. Pat. No. 5,608,306 e.g. discloses a system with a rechargeable battery pack including a real time clock and an application, whereby the battery pack is adapted to communicate real time data to said application. The real time data is generated on the basis of a counter value counting the oscillations of a crystal element provided in said battery pack. An additional pin is provided, which enables the transmission of the time data from the battery pack to the application. However, the proposed system suffers from the above-mentioned disadvantages.
The object of the present invention is therefore to provide a mobile terminal for a wireless telecommunication system, with a main body and a battery pack to be connected to the main body, said main body comprising a first frequency generating means for generating a first frequency information and a processing means for processing said first frequency information to provide a real time information, said battery pack comprising a second frequency generating means for generating a second frequency information and control means for controlling the transmission of said second frequency information to said processing means of the main body, whereby the processing means uses the second frequency information for providing updated real time information in the main body, which overcomes the above-mentioned disadvantages of the prior art and enables a reliable and accurate use of the second frequency information provided by a battery pack in the main body of the mobile terminal.
The above object is achieved by a mobile terminal for a wireless telecommunication system according to claim 1, comprising a main body and a battery pack to be connected to the main body, the main body comprising a first frequency generating means for generating a first frequency information and a processing means for processing the first frequency information to provide a real time information, said battery pack comprising a second frequency generating means for generating a second frequency information and control means for controlling the transmission of the second frequency information to the processing means, said processing means using said second frequency information for providing updated real time information, whereby the control means comprises a battery pack memory for storing first information relating to an update value of the second frequency information.
The use of a battery pack memory in which information relating to an update value of the second frequency information enables the processing means of the main body to determine, if the second frequency information provided by the battery pack is reliable and accurate. The update value can e.g. be a calibration value for the second frequency information or an information, that a calibration value is stored either in the battery pack or the main body. Thus, the mobile terminal according to the present invention is able to operate on the basis of a reliable and accurate time base at any time and under any circumstances. Further, the back up battery necessary in known mobile terminals can be omitted so that the main body becomes cheaper to produce and particularly the expensive disposal costs for disposing back up batteries under the corresponding European regulations are eliminated.
It is to be noted that the first frequency information generated by the first frequency generating means in the main body and the second frequency information generated by the second frequency generating means in the battery pack are oscillations of a crystal or quartz element comprised in the frequency generating means which are counted so that a count or clockcycle number is obtained. This number is accumulating with time and processed into a real time information in a known manner. Advantageously, the processing means comprises a main body memory for storing battery identity information, whereby each time a battery pack is connected to the main body, the processing means reads a battery pack identity information stored in the battery pack memory and checks if said read battery pack identity information is already stored in the main body memory. Hereby, the first information stored in the battery pack memory can be a calibration value for the second frequency information, whereby the calibration value is transmitted by the control means to said processing means and used by the processing means for providing updated real time information. Hereby, two advantageous possibilities are present. First, the calibration value can be stored in the battery pack memory when the battery pack is connected to the main body for the first time. In this case, the processing means in the main body performs a calibration of the second frequency information, e.g. on the basis of the highly accurate time base of the main body or through highly accurate time information input to the mobile terminal. Second, the calibration value can be prestored in the battery pack memory hereby the manufacturer of the battery pack memory can e.g. callibrate the second frequency information and store a corresponding calibration value in the battery pack memory. Storing of a calibration value in the battery pack memory has the advantage that in case that the battery pack is used with different mobile terminals, the calibration value stored in the battery pack memory can be supplied to the main body of the mobile terminal to be used for accurate and reliable real time information.
In an advantageous alternative, a or said main body memory of the processing means is adapted to store an update value of the second frequency information and said first information stored in said battery pack memory indicates if an update value of the second frequency information is stored in the main body memory. In this case, the information stored in the battery pack memory is a mere indication information relating to update information stored in the main body memory. Advantageously, if said battery pack is connected to the main body for a first time, the processing means performs a calibration of the second frequency information and stores a calibration value as said update value in the main body memory. Further advantageously, each time the battery pack is connected to the main body, the processing means checks if an update value is stored in the battery pack memory. Hereby, in case that the processing means detects that an update value is stored in the battery pack memory, it provides updated real time information on the basis of the update value stored in the main body memory. According to a further advantageous aspect, the battery pack memory can be adapted to store a second information indicating if a battery identification information and a second frequency information had been stored in the main body memory. Hereby, in case that the battery pack is disconnected from the main body, a last second frequency information is stored in the main body memory together with the battery pack identification information. This is advantageous when using different battery packs with one main body.
Further advantageously, the battery pack memory is adapted to store a third information indicating if the temperature level had been exceeded. Reading out this third information, a service station knows that the battery pack had been subjected to high temperatures, which could damage the capacity of the battery cells, so that corresponding countermeasures could be taken. Further advantageously, the battery pack memory is adapted to store a fourth information indicating if a wrong charging device had been connected to the main body to charge the battery pack. A wrong charging device could either be a defect charging device of the same manufacturer of the main body and the battery pack, or a charging device of a different manufacturer not corresponding to the charge requirements of the main body and the battery pack manufacturer.